The present invention relates to an alternator for a vehicle and more particularly, to a liquid-cooled alternator for a vehicle.
Most conventional automotive alternators are of an air-cooled type that dissipates heat generated therein into the atmosphere. Recently, the temperatures of parts arranged in an engine room have increased, and the temperature of air in the engine room has increased. Consequently, when the ambient air temperature rises, air-cooling cannot efficiently dissipate the heat generated by the alternator in some automobiles.
Although the heat generating ability of a regulator for regulating an automotive alternator is not high, it is important to cool the regulator efficiently because the absolute heat resistance of the regulator, as compared with that of stator coils, is not high.
Recently, automobiles are required to arrange parts in the engine room in a high density, to improve the efficiency of the engine and to reduce emissions for low noise and improvement of output and efficiency. Consequently, there is a tendency that the temperature in the engine room increases and radiant heat increases due to temperature rises in the parts disposed in the engine room. Therefore, an automotive alternator disposed in the engine room is exposed to a high-temperature atmosphere for a long time, which causes the deterioration of the performance and the shortening of the life of the automotive alternator.
A method of protecting the automotive alternator from heat damage disposes a heat shield plate formed of a material having low heat conductance between the automotive alternator and hot parts arranged in the engine room. However, the effect of this method in protecting the automotive alternator from heat damage is not satisfactory because air temperature in the engine room rises inevitably when the engine is operated continuously for a long time.
Liquid-cooled automotive alternators disclosed in JP 7-194060A and JP 2000-245111A are intended for use in a hot atmosphere.
Alternators disclosed in JP 7-194060A, EP 1041699A2 and EP 1096647A2 dissipate heat generated by a voltage regulator and a rectifier through a heatsink and a rear housing to cool the alternators. The alternator disclosed in JP 2000-245111A dissipates heat generated by a voltage regulator and rectifier through a heat-radiating plate, a rear bracket on a side opposite to the side of a pulley, a member having good heat conductance and a liquid-cooled housing to cool the alternator.
In the alternator disclosed in JP 7-194060A and JP 2000-245111A, the heatsink of the regulator must be in close contact with the rear housing and the rear bracket to water-cool the regulator. Consequently, the alternators are subject to restrictions on the arrangement of the regulator, the brushes and the rectifier, which causes structural inconvenience and problems with assembling work.